NASA, the National Reconnaissance Office (NRO) and the U.S. Air Force signed an agreement this week to establish clear criteria for certification of commercial providers of launch vehicles used for national security space and civil space missions.

Escape Velocity -- An escape velocity is the minimum speed at which an object without propulsion can move away from a source of a gravitational field indefinitely if there is no friction.
This definition may need modification for the practical problem of two or more sources in some cases. In any case, the object is assumed to be a point with a mass that is negligible compared with that of the source of the field, usually an excellent approximation. It is commonly described as the speed...